The present invention relates to a container for shipping nuclear fuel assemblies and particularly relates to an end support system for the outer wooden container for the nuclear fuel assemblies.
Containers are conventionally used to ship nuclear fuel assemblies. Typically, each container includes an inner metal box with two separate channels, each of which carries a single nuclear fuel assembly. Normally, a pair of such nuclear fuel assemblies are arranged in side-by-side relation within the inner metal box. The inner box with the fuel assemblies is typically packaged for shipment within an outer container formed of wooden framing elements, panels interconnecting the framing elements and fillers to prevent movement of the inner box relative to the outer container. The outer container is sealed with metal bolts and is also banded with metal straps.
It has become significant for meeting both domestic and international licensing requirements that the integrity of the outer container not be compromised as a result of certain drop and fire tests required by various licensing agencies. For example, licensing regulations require 4-foot and 30-foot drop tests in which the inner metal box must be completely contained within the wooden outer container during the drop tests. Recent drop tests have demonstrated failure of certain prior outer wooden containers to meet the requirements of these drop tests. Specifically, the inner metal box must not break out of or breach the outer wooden container during the drop tests. In preliminary tests, however, it has been observed that the ends of the wooden outer container do break out and no longer provide containment for the inner metal box actually containing the nuclear fuel assemblies. The wooden end frames at the ends of the wooden outer container appear particularly vulnerable to damage and, in certain cases, have broken away from the wooden container, exposing the inner metal box. Accordingly, there is a need for end support systems for nuclear fuel shipping containers which can absorb energy during the drop tests and contain damage to the container ends such that the shipping containers comply with various regulatory licensing requirements.
In accordance with a preferred embodiment of the present invention, there is provided an end support system for a nuclear fuel assembly shipping container which sufficiently maintains the integrity of the wooden container ends to meet the requirements of licensing regulations. To accomplish the foregoing, each end support system includes a metal end frame for overlying the wooden framing elements forming the ends of the wooden shipping container. It will be appreciated that the ends of the wooden container comprise rectilinear end frames formed of wooden framing elements, typically 2xc3x974s, each having a panel secured to the inside surface of the end frame. The end panels are conventionally formed of plywood. The wooden end frame is secured to longitudinally extending wooden structural framing elements formed along the sides, top and bottom of the container. Each end support system hereof includes a metal end frame formed of top, bottom and side metal plates secured to one another forming a rectilinear frame. A metal crosspiece extends between opposed plates, e.g., the side plates, and carries a reinforcing member engageable with the end panel of the container to reinforce the panel. Additionally, opposite ends of the reinforcing member engage the edges of the wooden framing members at opposite sides of the wooden end frames. With each metal end frame overlying the wooden end framing elements and secured thereto, for example, by a plurality of metal screws, the wooden end frame is substantially reinforced.
Additionally, at least four arms formed of metal plates are secured to the metal end frame. The arms extend in a perpendicular direction from the metal end frame for overlying opposite sides of the container along the longitudinally extending wooden structural framing elements. The arms, like the end frame, are secured to the wooden framing elements, for example, by a plurality of metal screws. The metal end frame and lateral support arms thus constitute an end support system for each of the opposite ends of the wooden container. Each end support system reinforces a container end ensuring its integrity and prevents breach of the container end sufficiently to comply with licensing regulations.
In a preferred embodiment according to the present invention, there is provided an end support system for a container for shipping nuclear fuel, comprising first and second elongated metal plates generally parallel to and spaced from one another and third and fourth metal plates generally parallel to and spaced from one another, the third plate being secured at opposite ends to ends of the first and second plates and the fourth plate being secured at opposite ends to opposite ends of the first and second plates thereby forming a generally rectilinear metal end frame, an elongated metal cross-plate secured at opposite ends to the third and fourth plates, respectively, at locations intermediate ends of the third and fourth plates, the cross-plate extending generally parallel to the first and second plates and lying generally in a plane defined by the metal end frame, a metal reinforcing member secured to the cross-plate and projecting from one side thereof and generally out of the plane, the member being located intermediate the opposite ends of the cross-plate and inwardly of the third and fourth plates and at least a pair of metal supports connected to the metal end frame and extending generally perpendicular to the end frame along opposite sides of the metal end frame for securement to the container.
In a further preferred embodiment according to the present invention, there is provided a container for shipping nuclear fuel, comprising an elongated container body having sides, a top and bottom and opposite ends, a metal end frame for reinforcing each of the opposite ends of the container body, each metal end frame comprising first and second elongated metal plates generally parallel to and spaced from one another and third and fourth metal plates generally parallel to and spaced from one another, the third plate being secured at opposite ends to ends of the first and second plates and the fourth plate being secured at opposite ends to opposite ends of the first and second plates thereby forming the metal end frame in a generally rectilinear configuration, an elongated metal cross-plate secured at opposite ends to the third and fourth plates, respectively, and at locations intermediate ends of the third and fourth plates, the cross-plate extending generally parallel to the first and second plates and lying generally in a plane defined by the metal end frame, a metal reinforcing member secured to the cross-plate and projecting from one side thereof and generally out of the plane, the member being located intermediate the opposite ends of the cross-plate and inwardly of the third and fourth plates, at least a pair of supports connected to the metal end frame and extending generally perpendicular to the end frame along opposite sides of the metal end frame for securement to the container, the metal end frames being secured, preferably by a plurality of metal screws, to the container body ends, respectively, with the supports straddling opposite sides of the container body ends.
In a still further preferred embodiment according to the present invention, there is provided a container for shipping nuclear fuel, comprising an elongated container body having sides, a top and bottom and opposite ends, a metal end frame for overlying and reinforcing each of the opposite ends of the container body and lying in a plane, the ends and the sides of the container body being formed at least in part of wooden framing elements, a reinforcing member secured to the metal end frame and projecting from one side of the metal end frame and generally out of the plane, the member being located intermediate opposite edges of the metal end frame, at least a pair of metal supports connected to the metal end frame and extending generally perpendicular to the metal end frame along opposite sides of the metal end frame for securement to the container, each of the metal end frame and supports being secured to the wood framing elements along the ends and sides of the container body, respectively, with the supports straddling opposite sides of the container body ends, the reinforcing member engaging at least a portion of the container body to reinforce the container body.